This invention relates to the field of polymer film coating compositions and, in particular, to pigmented, heat-sealable coating compositions for application to oriented mono- and multi-layer polyolefin films and to the oriented films coated with such compositions.
A variety of heat-sealable coating compositions for sheets and films are known. U.S. Pat. No. 2,350,292 describes a heat-sealable coating composition for cellulosic sheet such as glassine paper or cellophane which is compounded by dissolving at elevated temperature a cellulose ether, e.g., ethyl cellulose, a moistureproofing wax, e.g., spermaceti, a hard wax, e.g., carnauba wax, and/or a resin, e.g., an ester gum, in a solvent in an organic solvent. The coating composition can also contain finely divided powders of talc, magnesium carbonate, calcium carbonate, calcium sulfate, etc., dyestuffs, coloring matter, and the like.
U.S. Pat. No. 2,711,996 describes a heat-sealable film coating composition containing a vinylidene chloride copolymer, an ester wax slip agent, e.g., carnauba wax, a long chain aliphatic compound and finely divided calcium carbonate.
U.S. Pat. No. 2,898,237 describes a heat-sealable aqueous dispersion coating composition for polyethylene terephthalate packaging film containing a major amount of an ABS terpolymer and a minor amount of at least one of polyvinyl chloride, ammonium rosinate and a paraffin or micro-crystalline wax.
U.S. Pat. No. 3,695,923 describes an oriented, polymer film, e.g., one of polypropylene, having on at least one side thereof a primer coating based on an acrylate interpolymer and a mixture of carnauba wax and stearic acid and, applied to the primer coating, a moisture-vapor and gas barrier heat-sealable coating containing vinylidene chloride polymer/copolymer, clay and a wax such as carnauba wax.
U.S. Pat. No. 4,175,977 describes a pigmented thermoplastic hot-melt coating composition for application to cellulosic substrates. The coating composition contains a major amount of a pigment such as titanium dioxide, calcium carbonate, clays, zinc oxide, antimony oxide, talc, silica, or mixtures thereof, and a minor amount of a thermoplastic binder such as polyethylene, ethylene-vinyl acetate copolymers, ethylene-organic acid copolymers, ethylene-vinyl acetate-organic acid terpolymers, polypropylene, polystyrene, polyamides, paraffin wax, microcrystalline wax, polyterpene resins, and mixtures thereof.
U.S. Pat. No. 4,214,039 describes a packaging film structure comprising a polypropylene film substrate having a heat sealable vinylidene chloride polymer. Intermediate the polypropylene film and the vinylidene chloride polymer is a primer coat which consists of the reaction product of an acidified aminoethylated vinyl polymer and an epoxy resin. This primer coat significantly enhances the bond strength between the polypropylene and the heat sealable vinylidene chloride polymer.
U.S. Pat. No. 4,447,494 discloses an oriented multi-layer heat-sealable film structure which comprises (a) a polyolefin film substrate, e.g., polyethylene, polypropylene, polybutene, copolymers and blends thereof, and preferably, an isotactic polypropylene, coated on at least one side thereof with (b) a layer of a random copolymer of ethylene and propylene, (c) a primer layer on the random copolymer layer and (d) a heat-sealable vinylidene chloride polymer latex top coating on the primer layer.